package transientlibs.rlforj.los;
import java.util.List;
import java.util.Vector;
import transientlibs.rlforj.math.Point2I;
import transientlibs.rlforj.util.BresenhamLine;
/**
* Bresenham LOS.
* Tries to reach destination along first path. If
* obstacled, shifts to alternate path. If that is blocked,
* shift to first path again. Fails only if both are blocked
* at a point.
* @author sdatta
*
*/
public class BresOpportunisticLos implements ILosAlgorithm
{
private Vector<Point2I> path;
public boolean existsLineOfSight(ILosBoard b, int startX, int startY,
int x1, int y1, boolean calculateProject)
{
int dx=startX-x1, dy=startY-y1;
int adx=dx>0?dx:-dx, ady=dy>0?dy:-dy;
int len=(adx>ady?adx:ady) + 1;
if(calculateProject)
path=new Vector<Point2I>(len);
int[] px=new int[len], py=new int[len];
int[] px1=null, py1=null;
px1=new int[len]; py1=new int[len];
//Compute both paths
BresenhamLine.plot(startX, startY, x1, y1, px, py);
BresenhamLine.plot(x1, y1, startX, startY, px1, py1);
boolean los=false;
boolean alternatePath=false;
for(int i=0; i<len; i++) {
// Have we reached the end ? In that case quit
if(px[i]==x1 && py[i]==y1) {
if(calculateProject){
path.add(new Point2I(px[i], py[i]));
}
los=true;
break;
}
// if we are on alternate path, is the path clear ?
if(alternatePath && !b.isObstacle(px1[len-i-1], py1[len-i-1])) {
if(calculateProject)
path.add(new Point2I(px1[len-i-1], py1[len-i-1]));
continue;
} else
alternatePath=false;//come back to ordinary path
//if on ordinary path, or alternate path was not clear
if(!b.isObstacle(px[i], py[i])) {
if(calculateProject) {
path.add(new Point2I(px[i], py[i]));
}
continue;
}
//if ordinary path wasnt clear
if(!b.isObstacle(px1[len-i-1], py1[len-i-1])) {
if(calculateProject)
path.add(new Point2I(px1[len-i-1], py1[len-i-1]));
alternatePath=true;//go on alternate path
continue;
}
if(calculateProject)
path.add(new Point2I(px1[len-i-1], py1[len-i-1]));
break;
}
return los;
}
public List<Point2I> getProjectPath()
{
return path;
}
}